This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Radiation damage is a major problem at third-generation synchrotron light sources. This adversely affects the data quality of single crystal diffraction experiments. Although the mechanism of radiation damage is reasonably well understood, it is not clear how to alleviate the adverse effects of radiation damage on data quality. Free-radical scavengers are used in many cases, but there is no agreement on the usefulness of this method. While it is known that radiation damage is significantly less at LN2 temperature, there is no conclusive data on how much better it would it be at even lower temperatures. We are doing a systematic study of radiation damage as a function of temperature.